The European Food Safety Authority (EFSA) has said pregnant women should limit their intake of predatory fish such as swordfish and tuna due to the higher levels of mercury they contain.

"EFSA recommends that women of childbearing age (in particular, those intending to become pregnant), pregnant and breastfeeding women as well as young children select fish from a wide range of species, without giving undue preference to large predatory fish such as swordfish and tuna," the EFSA said.

Mercury is present as an environmental contaminant in foods, notably in fish and seafood principally in the form of methylmercury. Due to their place in the food chain, predatory fish such as tuna and swordfish are likely to contain higher levels of methylmercury than other fish species.

The European Food Safety Authority's (EFSA) Scientific Panel on Contaminants in the Food Chain (CONTAM) advised that further dietary studies be conducted among vulnerable population groups, including women of childbearing age and children, where specific intake data are lacking.

Following a request from the European Commission, the panel evaluated the possible risks to human health from the consumption of foods contaminated with mercury, in particular methylmercury, based on intake estimates for Europe.

The main source of human exposure to methylmercury from food is fish and seafood products. Given that the average intake estimates of methylmercury for European consumers are below but at times rather close to the provisional tolerable weekly intake (PTWI) established by the Joint FAO/WHO Expert Committee on Food Additives (1.6 µg/kg body weight) and some intake estimates exceed the limit established by the U.S. National Research Council (0.7 µg/kg body weight per week), the CONTAM panel recommended that a more complete evaluation of exposures be carried out in Europe.

"Above safe levels of intake, methylmercury is particularly toxic to the nervous system and developing brain. Exposure during pregnancy and early infancy is therefore of particular concern, and this is precisely where appropriate intake data are lacking," said Dr. Josef Schlatter, chair of the EFSA panel.

The EFSA added that fish is an important part of a healthy diet as it provides important nutrients.